The World Water Issues

Abstract

The chapter introduces to concepts and debates that dominate the water issue at the global scale. First, the world water balance outlines contributions made to the development of understanding renewable freshwater resources on Earth, as well as withdrawals and impact of human actions on the hydrological cycle. The water footprint concept applied at global scale makes it possible to specify the respective places occupied by blue, green and virtual water in the world budget. A second part focusses on water balance of arid countries. The following part deals with impacts of anthropogenic activities on water resources, particularly acute in arid countries where strategies of massive resource mobilization and transfers are faced with problems related to water scarcity and competing demands. The perspective of climate change exacerbates an already critical situation in some countries under water stress: increased exploitation, quality deterioration, overexploitation, soils and aquifers salinization, negative impacts of dam reservoirs on groundwater recharge. The last part presents the main principles, concepts and instruments of water policies. Among the basic principles should be mentioned the user pays and polluter pays principles, the precautionary principle and the principle of subsidiarity. As regards the instruments, different approaches are presented: integrated water resources management, water demand management, watershed-based management, participatory management. Mention is also made of aspects relating to the economic dimension of water, value and pricing, as well as water data and water information systems.